Litke, David W., 1999, Review of phosphorus control measures in the United States and their effects on water quality: U.S. Geological Survey Water-Resources Investigations Report 99-4007, 38 p. Available Online

Litke, David W., 1996, Sources and loads of nutrients in the South Platte River, Colorado and Nebraska, 1994-95: U.S. Geological Survey Water-Resources Investigations Report 96-4029, 31 p. Available Online

Maret, T.R., Konrad, C.P., and Tranmer, A.W., 2010, Influence of environmental factors on biotic responses to nutrient enrichment in agricultural streams: Journal of the American Water Resources Association, 16 p., on-line only in advance of print. doi: 10.1111/j.1752-1688.2010.00430.x Available Online

Maupin, M.A., and Ivahnenko, T., 2011, Nutrient loadings to streams of the continental United States from municipal and industrial effluent: Journal of the American Water Resources Association, online 22Aug2011 in advance of print, 15 p. doi: 10.1111/j.1752-1688.2011.00576.x Available Online

McMahon, P.B., 2000, A reconnaissance study of the effect of irrigated agriculture on water quality in the Ogallala Formation, central High Plains: U.S. Geological Survey Fact Sheet FS-009-00, 6 p. Available Online